1. Field of the Invention
The present invention relates to the field of impact driveable screws. In particular, the present invention relates specifically to an asymmetric thread screw having a ballistic point for use with impact drivers along with a high degree crest angle forming a long surface area slide flank and a short surface area grip flank to reduce fiber cutting during impact insertion of the screwnail. A secondary mushroom compaction thread is also disclosed.
2. Description of the Known Art
As will be appreciated by those skilled in the art, symmetrical thread screws, self drilling screws, and screws with cutting points have been known for an extended period of time. Present construction techniques use screws with a cutting or self tapping head that are rotated into a material to connect different materials together. This is very time consuming because of the extended time period it takes to rotate the screw into the material.
Other techniques use a combination of glue and regular nails in an attempt to achieve a similar holding power to the rotated screws. This creates a permanent attachment that cannot be disassembled. Similarly, the use of regular nails creates a strong bind that is difficult if not impossible to disassemble.
HITACHI has recently attempted impact driving screws with prior art type screw designs using a cutting point and a sharp angled thread on a wide thread pitch. These screws rip and tear the wood fibers during installation. See http://www.hitachipowertools.com for the limited information on their design.
Patents disclosing information relevant to screws include: U.S. Pat. No. 137,414, issued to Burdick on Apr. 1, 1873; U.S. Pat. No. 276,541, issued to Sloan on Apr. 24, 1883; U.S. Pat. No. 327,296, issued to McGinnis on Sep. 29, 1885; U.S. Pat. No. 373,074, issued to Jones on Nov. 15, 1887; U.S. Pat. No. 426,008, issued to Groff on Apr. 22, 1890; U.S. Pat. No. 471,179, issued to Jones on Mar. 22, 1892; U.S. Pat. No. 676,240, issued to Latty on Jun. 11, 1901; U.S. Pat. No. 1,326,910, issued to Butterfield on Jan. 6, 1920; U.S. Pat. No. 1,891,895, issued to Nagel on Dec. 20, 1932; U.S. Pat. No. 1,912,222, issued to Rosenberg on May 30, 1933; U.S. Pat. No. 1,953,592, issued to Deniston on Apr. 3, 1934; U.S. Pat. No. 2,001,869, issued to Deniston on May 21, 1935; U.S. Pat. No. 2,046,837, issued to Phillips on Jul. 7, 1936; U.S. Pat. No. 2,075,411, issued to Mertens on Mar. 30, 1937; U.S. Pat. No. 2,093,610, issued to Kraemer on Sep. 21, 1937; U.S. Pat. No. 2,190,883, issued to Pauze on Feb. 20, 1940; U.S. Pat. No. 2,269,708, issued to Dickson on Jan. 30, 1942; U.S. Pat. No. 2,558,379, issued to Phipard on Jun. 26, 1951; U.S. Pat. No. 2,605,867, issued to Goodwin on Aug. 5, 1952; U.S. Pat. No. 2,967,448, issued to Hallock on Jan. 10, 1961; U.S. Pat. No. 3,010,353, issued to Psaros on Nov. 28, 1961; U.S. Pat. No. 3,019,460, issued to Corckram on Feb. 6, 1962; U.S. Pat. No. 3,056,234, issued to Nelsson et al. on Oct. 2, 1962; U.S. Pat. No. 3,204,516, issued to Wieber on Sep. 7, 1965; U.S. Pat. No. 3,850,073, issued to Hayes on Nov. 26, 1974; U.S. Pat. No. 3,861,527, issued to Perkins on Jan. 21, 1965; U.S. Pat. No. 3,977,142, issued to Dove et al. on Aug. 31, 1976; U.S. Pat. No. 4,572,720, issued to Rockenfeller et al. on Feb. 25, 1986; U.S. Pat. No. 4,718,802, issued to Rockenfeller, et al. on Jan. 12, 1988; U.S. Pat. No. 4,932,820, issued to Schniedermeier on Jun. 12, 1990; U.S. Pat. No. 5,375,957, issued to Golledge on Dec. 27, 1994; and U.S. Pat. No. 5,741,104, issued to Lat et al. on Apr. 21, 1998. Each of these patents is hereby expressly incorporated by reference in its entirety. These prior art references teach that screws should cut the wood fibers with a cutting or pyramid shaped point during insertion. Thus, it may be seen that these prior art patents are very limited in their teaching and utilization, and an improved impact driveable screwnail is needed to overcome these limitations.